The present invention relates to a control system which integrates a machine controller for real time steering of the a machine over a learned path and a GPS or Gyro based monitor for monitoring the precision of the steering and correcting any drift away from the learned path as the machine operates. In an illustrated embodiment an on board controller communicates with other selected machines (such as mowers in the field) such that a plurality of machines operate together to complete a task (such as a plurality of mowers within the same field).
An illustrated embodiment of the present invention includes a control system which integrates a servo machine controller for real time steering of a machine with machine vision, which “sees” previously delivered markers that define the path of travel of the machine and other machine commands encoded within parameters of the marker. Initial markers are illustratively used to define the outer limits of the operating area. The machine will then follow those markers while doing work such as mowing, plowing, planting, etc. As the machine travels, it delivers a new marker path, which defines the next path for the machine to follow. This process continues until the work within the defined area is complete. A specific color or other defining parameter of the markers may illustratively be used to encode various commands to the machine such as the outer limits, follow, turn points, speed changes, pause, shut down, reverse, read compass etc. Each defining parameter in the marker can encode a given command to the controller via the vision system. Some markers can contain more than one parameter difference thus more than one machine command.
Another illustrated embodiment of the present invention includes a control system which integrates a servo machine controller for real time steering of the a machine over a learned path, machine vision which “sees” markers as discussed above, and a GPS based monitor for monitoring the precision of the steering and correcting any drift away from the learned path as the machine operates. The markers are “seen” by the on-board machine vision. The markers are used to encode various commands to the machine such as the outer limits of the field, follow, turn points, speed changes, pause, shut down, reverse, read compass etc. The on board controller also may communicate with other selected machines in the area enabling a team of machines to operate together.
The preferred embodiment of the invention is the integration of the control system with a Zero Turning Radius (ZTR) lawn mower. While the ZTR lawn mower embodiment is described herein, it is understood that other vehicles and machines may include the control systems of the present invention described herein. For example in other embodiments the control system may be used with farm tractors, trucks, bulldozers, utility transports, military vehicles and tanks, other types of mowers, etc. the control systems of the present invention described herein may also be used to guide motor vehicles on the roads or guide boats along desired paths. In the boating application, the boat can be programmed to avoid hidden obstacles in the water by maintaining the boat on the predetermined path.
This control system has wide usage in application where on board operators are used to operate the machine but there is a desire to replace the operator with a robotic machine for reasons such as cost, safety, efficiency, shortage of operators, reliability of operators, harsh impact of the mowing debris on the operator or other variables that impact the overall operation of the machine. In order words, the machine may be operated in both manual and automatic modes.
Basic Operation of a ZTR Mower:
Presently a person must drive the lawn mower to complete the lawn-mowing task in both the commercial and domestic markets. The preferred mower in the both markets is the ZTR mower.
Two hydraulic motors power the ZTR mower, one on each rear driving wheel. Each motor/drive wheel will turn in either CW or CCW direction as the control valve is manually operated by the driver of the mower. Two vertical hand levers, one for each drive wheel, are positioned so the driver of the mower can easily access and operate them directing the hydraulic control valve to route the hydraulic oil which powers the hydraulic motors to turn either CW or CCW at a rate and direction that is controlled by the position of the vertical hand levers. These levers control the direction and speed of the mower.
Robotic ZTR Mower:
The robotic mower is the integration of a multiplicity of sub-systems with a ZTR mower. These sub-systems include: a servo motion controller to control various sections of the mower such as the steering, speed, blades and engine, a vision system used to track ground based command markers, a compass to enable the robot to have directional capability, a GPS system to monitor location, a communication system to receive and send data to other robots or base stations, a computer to store data, store programs and control the entire robotic system, various sensors to measure distances to objects and various mower and engine parameters and a system that delivers ground based command markers.
Basic Operation of a RZTR (Robotic Zero Turning Radius) Mower:
The computer-based controller allows the RZTR of the present invention to be operated in two separate modes. The first mode is the learn mode where the robotic mower either learns a path and stores the path in a computer to be used for future operation of RZTR or deliver(s) ground based markers creating an initial path for immediate use by the RZTR.
The second mode of operation depends upon how the RZTR was programmed. If the RZTR was programmed in the learn mode then any properly equipped RZTR can use this program to operate alone in a field or as a member of a team of RZTR's mowing the field.
If the RZTR initially delivered markers then any properly equipped RZTR can follow the markers while delivering additional tracking markers as the field is being mowed.
The first mode of operation allows the operator to drive the RZTR in a normal manual mode. In this mode the operator can direct the controller to learn and save the path over which the mower is being drive and/or deliver ground based command markers. Each drive wheel has an encoder attached. The mowing path is “learned” by the computer recording the data coming from each encoder. A servo controller is attached to each wheel control valve. In the robotic mode the computer steers the mower by utilizing the stored path data to activate each of the control valves via the servo attached to the valves. This control function will steer the mower over substantially the same learned path stored in the memory of the computer as the operator steered the mower over the original path.
Variables exist in the total system such as tire pressure, roughness of the terrain, slippage of both wheels and other system variables. These variables may result in the mower slowly drifting off the original learned mowing path. This drift may be corrected periodically by utilizing GPS coordinate data or machine vision system data generated by tracking the ground based markers. The stored path data in the computer steers the mower and the GPS monitors the exact location providing means for correcting the drift inherent in the system. The compass is used to set a direction from a random starting point to the beginning of the stored mowing path. The compass may also provide direction information during operation enabling the computer to anticipate major direction changes. The compass may also provide a monitoring function by checking direction of the mower against the learned path.
Basic Operation of a ZTR Robotic Mower Utilizing Machine Vision Path Monitoring:
This system follows a path of targets or visual markers that are delivered from the mower as an operator steers a path around an area of a field that is to be mowed. Once the perimeter is completed the operator switches the mower to robotic mode to complete the mowing of the area. In this mode the mower uses the on board machine vision to find the next target or marker and steer the mower toward that marker. The mower is steered between markers by the same servo control system described above. This process will continue until the encircled area has been mowed.
This robotic mower can also be used to mow a pattern in which the mower reverses direction at each end of the cut and follows the same previous cut, but in the opposite direction. Illustratively, a different colored marker is delivered at the end of the each cut signaling a turn around. This process continues until the entire area is mowed.
In another embodiment, the area to be mowed is encircled delivering a path of turn around markers. When the perimeter is defined in this manner the operator will cut a path along one edge of the area delivering a row of guidance markers then change the mower into the robotic mode preparing the mower to finish mowing the remaining defined area. The mower will follow the guidance markers along the first cut until finding a turn around marker then the mower will turn around reversing direction and follow the guidance markers until finding another turn around marker. This process continues until the area has been completely mowed and the end marker is encountered. In both types of cut patterns an end marker will be planted in the field area such that when this marker is reached the mower shuts down.
In all the above-described mowers proximity sensors or other types of anti-collision sensors such as radar, laser scanners, or RF Antennas, etc. are used to avoid a collision of the mower and other objects.
In an illustrated embodiment of the present invention, a method of moving a machine along a desired path includes operating a machine in a manual mode to traverse the desired path, the machine having at least one drive wheel and a steeling wheel, recording control signals to the at least one drive wheel and the steering wheel as the machine traverses the desired path during the manual mode to provide stored path data, detecting GPS location signals at a plurality of locations along the desired path during the manual mode, and storing a plurality of GPS locations which are linked to particular points along the desired path. The method also includes operating the machine in a robotic mode in which the stored path data is used to control the at least one drive wheel and the steering wheel to move the machine along the desired path without operator control, detecting GPS location signals at a plurality of locations along the path traveled by the machine during the robotic mode, comparing the GPS location signals at a plurality of locations along the traveled path during the robotic mode with the corresponding stored GPS locations that were linked to particular points along the desired path during the storing step, and correcting the position of the machine if it is determined that the machine has moved away from the desired path by a predetermined amount based on the comparing step.
In another illustrated embodiment of the present invention, a self-propelled vehicle includes a frame, a plurality of wheels coupled to the frame, and a hydraulic motor supported by the frame. The hydraulic motor is coupled to at least one drive wheel selected from the plurality of wheels to provide power to rotate the at least one drive wheel. The vehicle also includes a hydraulic control valve coupled to the hydraulic motor, and a stepper motor coupled to the hydraulic control valve. The stepper motor is configured to adjust an output from the hydraulic control valve to control the hydraulic motor and adjust the speed and direction of rotation of the at least one drive wheel.
In one illustrated embodiment, the hydraulic control valve includes a rotatable control shaft configured to adjust an output of the hydraulic control valve. The stepper motor is coupled to the control shaft to selectively rotate the control shaft in first and second directions to adjust the speed and direction of the at least one drive wheel.
In yet another illustrated embodiment of the present invention, a method of moving a machine along a desired path includes storing path data indicating a desired path of travel for the machine, storing a plurality of GPS locations linked to particular points along the desired path, automatically moving the machine along the desired path using the stored path data, and detecting GPS location signals at a plurality of locations along the path actually traveled by the machine during the automatically moving step. The method also includes transmitting a GPS reference signal to the machine, determining a corrected GPS location at each of the plurality of locations along the path actually traveled by the machine based on detected GPS location signals and the GPS reference signal, and comparing the corrected GPS location at each of the plurality of locations along the path actually traveled by the machine with the corresponding stored GPS location that was linked to particular points along the desired path. The method further includes correcting the position of the machine if it is determined that the vehicle has moved away from the desired path by a predetermined amount based on the comparing step, and charging a fee based on usage of the GPS reference signal.
In one illustrated embodiment, the method includes transmitting information related to the machine from the machine to a remote computer. The information transmitted from the machine to the remote computer may include identification data for the machine. The remote computer validates the machine based on the identification data and records an amount of time that the validated machine is receives the GPS reference signal.
In still another illustrated embodiment of the present invention, a method of moving at least two machines along a desired path includes storing path data indicating a desired path of travel for the at least two machines, providing at least two machines located at different positions on the desired path, and automatically moving the at least two machines simultaneously to traverse the desired path using the stored path data.
In an illustrated embodiment, a first machine is a master machine and at least one other machine is a slave machine. The master machine may communicate the stored path data to the at least one slave machine. The master machine may also communicates stored GPS locations linked to particular points along the desired path to the at least one slave machine.
In a further illustrated embodiment of the present invention, a method of moving a machine along a desired path includes storing path data indicating a desired path of travel for the machine, storing a plurality of GPS locations linked to particular points along the desired path, automatically moving the machine along the desired path using the stored path data, and detecting GPS locations at a plurality of locations along the path actually traveled by the machine during the automatically moving step within an accuracy of about 30 cm or less without the use of a GPS reference signal to correct the detected GPS location signals. The method further includes comparing the detected GPS location at the plurality of locations along the path actually traveled by the machine with the corresponding stored GPS location that were linked to particular points along the desired path, and correcting the position of the machine if it is determined that the vehicle has moved away from the desired path by a predetermined amount based on the comparing step.
In one illustrated embodiment, the step of detecting GPS locations at a plurality of locations along the path actually traveled by the machine uses a single multi-frequency GPS receiver on the machine. In another illustrated embodiment, the step of detecting GPS locations at a plurality of locations along the path actually traveled by the machine uses a plurality of single frequency GPS receiver on the machine. As discussed above, it is understood that these guidance systems can be implemented on other types of mowers requiring different control system designs but still using the same guidance concepts.